U.S. Pat. No. 4,951,188 discloses a control arrangement which controls an electric motor via at least one switching element with clocked drive signals. A switching arrangement is located between a computer unit generating the control signals and the electric motor. The circuit arrangement includes a first circuit unit in addition to the at least one switching element. The first circuit unit acts as a voltage increasing circuit for driving the at least one switching element. Here, a capacity is charged which leads to an increase in voltage at the drive input of the at least one switching element via the operating voltage of the circuit arrangement. The known circuit arrangement includes additional circuits such as current detecting elements, voltage controller circuits as well as a diagnostic circuit for monitoring current in the area of the motor or the switching elements.
However, in U.S. Pat. No. 4,951,188 no measures are described with respect to the following: preventing the control of the electric motor in the event of faults in the computer unit; providing protection against defective drives; providing measures which are suitable for protection against reversed polarity; or, protecting overloaded components or overloaded entire circuits during overvoltage conditions. In motor vehicles, electric motors are increasingly used as actuators even in safety-relevant control systems such as drive-slip control systems or electronic gas pedal systems. For this reason, high requirements as to operational safety, availability and complexity are imposed on the circuit arrangement controlling the electric motors in dependence upon the drive signals generated in a computer unit. These requirements relate especially to the following points: resistance to short circuits; protection against polarity reversals; load-dump protection (protection of circuits when a battery clamp is separated); latching against defective functions; reduced component complexity and low cost; direct drivability from a computer element; mid to high power capability at low inherent loss; and, reduced disturbance spectrum caused by radiation.
As described above, these requirements can at least in part not be fulfilled by known circuit arrangements.